The invention relates to a regenerative post-combustion apparatus, which in a housing comprises from top to bottom:
a) a combustion chamber;
b) a heat exchanger area, which is subdivided into a plurality of segments filled with heat exchanger material;
c) a rotating distributor, which depending on its rotational position establishes:
ca) a connection between an inlet for waste gas to be cleaned and at least one first segment of the heat exchanger area;
cb) a connection between at least one second segment of the heat exchanger area and an outlet for cleaned gas,
wherein a device for thermal regeneration of the heat exchanger material is provided, by means of which hot clean gas may be conveyed through selected segments of the heat exchanger area until the impurities, which have become attached to the heat exchanger material, detach from the latter.
Regenerative post-combustion apparatuses are used to clean contaminated waste gases from industrial processes. To save energy during the thermal post-combustion, the waste gases to be cleaned are conveyed through heat exchanger materials. As the waste gases to be cleaned frequently contain impurities, in particular also organic impurities in the form of condensable substances, e.g. tar products, or dusts, in the course of operation the surfaces of the heat exchanger materials become clogged with said impurities. For regeneration, the heat exchanger material periodically has to be heated up to a temperature, at which the impurities attached to the surface detach themselves and may be removed. In the present context, by xe2x80x9cattachedxe2x80x9d impurities are meant all impurities which may attach to the heat exchanger material mechanically, chemically, through absorption, through adsorption or through condensation processes and may be removed by a thermal process combined with flow.
This occurs in the known thermal post-combustion apparatuses in that their normal operation, during which the waste gases are cleaned, is interrupted. Hot gases, which may originate e.g. from the combustion chamber, are conveyed through the individual segments of the heat exchanger material until said segments have been heated from top to bottom up to the required temperature so that all regions of the heat exchanger material in said segments are freed of impurities. The drawback of said known regenerative post-combustion apparatuses is that normal operation has to be suspended for regeneration. Thus, if a continuous cleaning operation is to be ensured, it is necessary to provide, for the downtimes of the one regenerative post-combustion apparatus, a second post-combustion apparatus lying parallel thereto.
The object of the present invention is to refine a regenerative post-combustion apparatus of the type described initially in such a way that it enables a continuous cleaning operation also during thermal regeneration of the heat exchanger material.
Said object is achieved according to the invention in that the device for thermal regeneration comprises:
d) a burn-out rotary slide valve, which is disposed above the rotating distributor and comprises segments separated by dividing walls, wherein
da) at least one of the segments of the burn-out rotary slide valve is open in an upward direction and closed in the direction of the rotating distributor and communicates with an outlet, while
db) the other segments of the burn-out rotary slide valve are open in an upward and downward direction;
e) a driving device, by means of which the burn-out slide valve may be rotated in such a way underneath the heat exchanger area that its downwardly closed segment may be brought selectively into communication with each segment of the heat exchanger area.
In a post-combustion apparatus according to the invention, therefore, the gas flow from the rotating distributor into the segmented heat exchanger area filled with heat exchanger material is controlled by an additional element, the xe2x80x9cburn-out rotary slide valvexe2x80x9d. The latter in no way alters the basic mode of operation as regards waste gas cleaning compared to prior art; the only difference is that the flow path from the rotating distributor into the heat exchanger area is slightly longer compared to prior art. However, with the post-combustion apparatus according to the invention it is possible to remove an individual segment or individual segments of the heat exchanger area from the waste gas cleaning operation. For said purpose, the burn-out rotary slide valve is rotated in such a way that its downwardly closed segment communicates with the segment or segments of the heat exchanger area which is/are to be thermally regenerated. The latter is/are then no longer periodically cooled by a supply of cool outgoing air. It is or they are then heated from top to bottom by the hot gas used for thermal regeneration, which is conveyed either from the combustion chamber of the regenerative post-combustion apparatus via the relevant segments of the heat exchanger area to be regenerated and via the downwardly closed segment of the burn-out slide valve to the outlet or in the reverse direction. In either case the gases, which flow through the segments of the heat exchanger area to be regenerated and through the downwardly closed segment of the burn-out slide valve, are ultimately conveyed (once more) into the combustion chamber where the impurities, which have detached from the heat exchanger material during the regeneration process, are burnt. Said operation may, where required, be carried out separately for each segment of the heat exchanger area.
When the number of segments of the heat exchanger area corresponds to the number of segments of the burn-out rotary slide valve, this means that there is always one of the segments of the heat exchanger area which is unable to participate in the waste gas cleaning operation. This is avoided in the particularly advantageous embodiment of the invention, in which the heat exchanger area is subdivided into n segments and
a) the burn-out rotary slide valve is subdivided into (n+1) segments, of which n are open in an upward and downward direction and one is open in an upward direction and closed in a downward direction;
b) provided in the flow path between the burn-out rotary slide valve and the heat exchanger area is a transfer area, which
ba) at its top side is subdivided into n sectors, which each enclose an angle of 360xc2x0/n and have a through-opening, which communicates with one of the n segments of the heat exchanger area;
bb) at its bottom side is subdivided into (n+1) sectors, which each enclose an angle of 360xc2x0/(n+1), wherein n of said sectors have a through-opening, which depending on the rotational position of the burn-out rotary slide valve may communicate with each of the latter""s (n+1) segments, while one sector is closed and in a specific rotational position of the burn-out rotary slide valve is positioned above the latter""s downwardly closed segment;
bc) has n dividing walls, which in part extend obliquely in such a manner from the top side to the bottom side of the transfer area that the latter is subdivided into n segments, which at the top and bottom side each have a through-opening, wherein at least one of said segments at its bottom side is delimited at least partially by the closed sector.
The fact, that in said embodiment of the invention the burn-out rotary slide valve has one segment more than the heat exchanger area, allows the burn-out rotary slide valve to have just as many upwardly and downwardly open segments, i.e. segments participating in the waste gas cleaning operation, as the heat exchanger area. By virtue of the trick of the so-called xe2x80x9ctransfer areaxe2x80x9d the transition is provided between the segment arrangement, such as the heat exchanger area has, and the segment arrangement provided in the burn-out rotary slide valve. The transfer area at its bottom side with the closed sector provides a surface, under which the downwardly closed segment of the burn-out rotary slide valve may be xe2x80x9cparkedxe2x80x9d when there is to be no thermal regeneration in any segment of the heat exchanger area.
It is advantageous when the burn-out rotary slide valve comprises a central tubular piece, the interior of which communicates via an opening in its lateral surface with the downwardly closed segment of the burn-out rotary slide valve. The hot gas used for thermal regeneration is in said case supplied to, or discharged from, the burn-out rotary slide valve via the central tubular piece.
The central tubular piece of the burn-out rotary slide valve may be closed in a downward direction and communicate at the top with a coaxial central tubular piece of the above-lying component, which communicates with the connection. This means that the hot gas used for thermal regeneration is supplied from above to the burn-out rotary slide valve and discharged from the latter in an upward direction.
Alternatively, it is also possible for the central tubular piece of the burn-out rotary slide valve to be closed in an upward direction and communicate at the bottom with a coaxial central tubular piece of the component below, which communicates with the connection.
Which of the two latterly described embodiments of the invention is used will depend upon the geometric proportions of each individual case.
A further possibility of conveying the hot gas used for thermal regeneration through the burn-out rotary slide valve is such that the downwardly closed segment of the burn-out rotary slide valve has in its lateral surface an opening, via which it communicates with a stationary annular channel, which surrounds the burn-out rotary slide valve and in turn communicates with the connection. In said refinement of the invention, the hot gas used for thermal regeneration is supplied to, and discharged from, the burn-out rotary slide valve radially, which in individual cases is preferable likewise for geometric reasons.